The present invention relates to a detection means and, more particularly, to a proximity switch adapted to be threaded into a pressure cylinder wall, with the switch including a sensor portion insertable into a bore or perforation provided in the cylinder wall, with the sensor portion detecting a position of the piston.
It has been proposed to provide a proximity switch of the aforementined type with a synthetic resin housing; however, under practical conditions, considerable problems and disadvantages are encountered in connection with a sealing of the bore or perforation in the cylinder wall.
Moreover, in the proposed proximity switches, problems arise due to the frequently extremely high pressure within the cylinder which can lead to an improper deformation or, in extreme cases even to a blasting away of the entire proximity switch from the pressure cylinder.
Furthermore, the proposed proximity switches do not lend themselves to alignment during sassembly in each case and, consequently, the connecting cables of the proximity switches, which are generally lead or extend laterally away from the proximity switches, cannot be oriented into a position optimally adapted to a respective installation situation.
The aim underlying the present invention essentially resides in providing a proximity switch of the aforementioned type which is capable of withstanding a high pressure load, forming a secure seal, and is readily adapted to be rotationally aligned during assembly in an infinitely variable fashion in the cylinder wall about a longitudinal axis of the bore or perforation in the cylinder wall.
In accordance with advantageous features of the present invention, a housing of the proximity switch includes a metal casing means for accommodating a sensor part of the proximity switch, with a front cap means being provided for sealing the metal casing. A separate housing section is attached to the metal casing and includes the cable connection means. The metal casing has a continuously extending outer collar at a rear end thereof, with the collar being adapted to be fixedly clamped against the cylinder wall by a mounting gland means extending behind a rear face of the collar or by a coupling ring.
By virture of the above noted features of the present invention, the sensor part of the proximity switch and the metal casing surrounding the sensor part can be made of a very small diameter so that only a correspondingly small opening or bore in the cylinder wall is required and an end face of the sensor part, exposed to the pressure, is also of a small dimension. Consequently, the pressure load on the sensor part is considerably reduced by virtue of the features of the present invention.
Since the outer collar of the casing lying outside of the perforation can be constructed with a small wall thickness in accordance with the present invention, as well as with a large diameter, the collar can withstand maximum compressive forces and, respectively, tensile forces. The externally located housing section is no longer subjected to compressive or tensile stresses by virture of the present invention so that the mounting means between the casing and the external housing section poses no particular problems.
In accordance with additional further features of the present invention, the casing includes a rearward extension provided with an external thread adapted to receive the threadable portion of the housing section so as to enable the housing section to be threaded thereon. With such an arrangement, the outer collar of the casing and the housing section form between them a continuously extending external groove space wherein the mounting gland and/or the coupling ring is held in a loosely rotatable fashion.
In the industrial manufacturing of the proximity switch, the casing and the housing section are threaded together holding the mounting gland or coupling ring therebetween the free interspaces thereof are filled with a castable synthetic resin. During the step of mounting the proximity switch to the pressure cylinder, the metal casing is pushed into the opening or bore of the cylinder wall and, thereafter, the gland is initially loosely threaded in the prepared mounting bores of the pressure cylinder and, after a final rotary alignment of the proximity switch, it is fixedly clamped against the cylinder in the final step.
Advantageously, in accordance with the present invention, an outer collar of the casing and the housing section form therebetween a continuously extending external groove means for accommodating the mounting gland and or a coupling ring held therein in a loosely rotatable fashion.
A front cap of the metal casing accommodating the sensor part, advantageously is formed of one of a synthetic resin or a ceramic material.
Preferably, an annular groove with an O-ring inserted therein is provided in the front face of the outer collar and, advantageously, the sensor part has a mushroom-shaped core with a base in contact with the front cap, and with the mushroom-shaped core resting at a rearward portion thereof by way of a bushing on an inner shoulder of the metal casing.
Advantageously, in accordance with the present invention, the bushing includes a peripheral groove having an O-ring inserted therein which is adapted to be pressed against the metal casing, and a tubular projection surrounds the head of the mushroom-shaped core, with the front cap being inserted, with a rearward rim section, between the metal casing and the projection.
Advantageously, one locking shoulder or locking seat cooperating as a snap or click-stop connection is arranged at the rim section and at the projection of the bushing, respectively.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purposes of illustration only, one embodiment in accordance with the present invention.